Expression of the mdr1 gene may be an important cause of chemotherapy failure in patients with Non-Hodgkin's Lymphoma. ONCEP (Vincristine (0), Novantrome (N), Cyclophophamide (C), Etoposide (E), and Prednisone (P)) chemotherapy contains three MDR (Multi-drug resistance) -related agents (ON, E) and was designed for studies of MDR modulation. PC 833 is a non-immunosuppressive cyclosporine with greater in vitro MDR modulating activity that Cyclosporin A. ONCEP-PSC chemotherapy is well tolerated and has significant activity in patients with recurrent or refractory NHL.